Gas-Phase Alloying and Sintering Kinetics of 3D Printed Ni Scaffolds

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The fabrication of metal parts with increasingly complex geometries is of interest to several industries. In particular, metal scaffolds are good candidates for a variety of applications from batteries to biomedical implants, due to their low density and high surface area. However, many technologically important alloys are difficult to fabricate in scaffold geometries using traditional manufacturing, and even newer approaches such as additive manufacturing (often known as 3D printing), have significant challenges. A new process has been theorized for making these metal scaffolds through a two-step approach, which will enable an assortment of different materials to be produced from the same precursor printed metal part. This award supports research to understand the fundamental mechanisms of kinetics and thermodynamics that control this new process. Because of the wide range of engineering applications for metal scaffold structures, results from this research will promote technological innovations in a number of manufacturing sectors including energy, automotive and biomedical industries. Through recruiting and outreach activities, traditionally underrepresented groups in STEM will be involved in this research effort, which will engage students at an early age and help diversify the engineering career pipeline.While the ability to create near-net-shape metallic parts with high geometric complexity has made powder-bed additive manufacturing techniques attractive, many engineering relevant alloys are difficult to fabricate with high quality due to poor sintering, internal porosity, and cracking. One alternative approach is to decouple the printing and alloying by using particle-based ink printing to create the desired geometry from a pure metal or simple alloy that is known to print successfully, and then further alloy the part in a separate step using a deposition process and homogenization to reach the target composition. This approach is ideal for creating metallic scaffolds, taking advantage of the open porosity and small diffusion distances. The overall aim of this project is to study the fundamental sintering and alloying kinetics of such scaffolds using a combination of conventional metallography and in situ X-ray tomographic microscopy. The phase and pore evolution will be systematically studied as a function of geometry, composition, powder and strut size, and anneal time and temperature and the mechanical behavior will be computationally predicted and experimentally determined.